Comment.

[pintos-anon] / TODO

diff --git a/TODO b/TODO
index dbafb18c0b9820b18da094dfea98b6abcc4d0055..38836157fc052fe3a07b91d5d03bea94c64ac104 100644 (file)
--- a/TODO
+++ b/TODO
@@ -7,11 +7,6 @@ that span multiple pages, where some are mapped and some are not.
 An implementation that only checks the first page, rather than all pages 
 that can be touched during a call to read()/write() passes all tests.
 
 An implementation that only checks the first page, rather than all pages 
 that can be touched during a call to read()/write() passes all tests.
 

-- In Project 2, we're missing a test that would fail if they assumed
-that contiguous user-virtual addresses are laid out contiguously 
-in memory.  The loading code should ensure that non-contiguous 
-physical pages are allocated for the data segment (at least.)
-

 - Need some tests that test that illegal accesses lead to process
 termination. I have written some, will add them. In P2, obviously, 
 this would require that the students break this functionality since 
 - Need some tests that test that illegal accesses lead to process
 termination. I have written some, will add them. In P2, obviously, 
 this would require that the students break this functionality since 


@@ -26,123 +21,6 @@ Add a system call "get_kernel_memory_information".  User programs
 could engage in a variety of activities and notice leaks by checking
 the kernel memory statistics.
 
 could engage in a variety of activities and notice leaks by checking
 the kernel memory statistics.
 

----
-
-From: "Godmar Back" <godmar@gmail.com>
-Subject: priority donation tests
-To: "Ben Pfaff" <blp@cs.stanford.edu>
-Date: Fri, 3 Mar 2006 11:02:08 -0500
-
-Ben,
-
-it seems the priority donation tests are somewhat incomplete and allow
-incorrect implementations to pass with a perfect score.
-
-We are seeing the following wrong implementations pass all tests:
-
-- Implementations that assume that the priority of a thread waiting on
-a semaphore or condition variable cannot change between when the
-thread was blocked and when it is unblocked. The students implement
-this by doing an insert into an ordered list on block, rather than
-picking the maximum thread on unblock.
-
-Neither of these two cases is detected; do you currently check for
-these mistakes manually?
-
-I also wrote a test case for the second scenario:
-http://people.cs.vt.edu/~gback/pintos/priority-donate-sema.c
-http://people.cs.vt.edu/~gback/pintos/priority-donate-sema.ck
-
-From: "Godmar Back" <godmar@gmail.com>
-Subject: multiple threads waking up at same clock tick
-To: "Ben Pfaff" <blp@cs.stanford.edu>
-Date: Wed, 1 Mar 2006 08:14:47 -0500
-
-Greg Benson points out another potential TODO item for P1.
-
-----
-One thing I recall:
-
-The alarm tests do not test to see if multiple threads are woken up if
-their timers have expired.  That is, students can write a solution
-that just wakes up the first thread on the sleep queue rather than
-check for additional threads.  Of course, the next thread will be
-woken up on the next tick.  Also, this might be hard to test.
-
----
-Way to test this: (from Godmar Back)
-
-Thread A with high priority spins until 'ticks' changes, then calls to
-timer_sleep(X), Thread B with lower priority is then resumed, calls
-set_priority to make its priority equal to that of thread A, then
-calls timer_sleep(X), all of that before the next clock interrupt
-arrives.
-
-On wakeup, each thread records wake-up time and calls yield
-immediately, forcing the scheduler to switch to the other
-equal-priority thread. Both wake-up times must be the same (and match
-the planned wake-up time.)
-
-PS:
-I actually tested it and it's hard to pass with the current ips setting.
-The bounds on how quickly a thread would need to be able to return after
-sleep appear too tight.  Need another idea.
-
-From: "Godmar Back" <godmar@gmail.com>
-
-For reasons I don't currently understand, some of our students seem
-hesitant to include each thread in a second "all-threads" list and are
-looking for ways to implement the advanced scheduler without one.
-
-Currently, I believe, all tests for the mlfqs are such that all
-threads are either ready or sleeping in timer_sleep(). This allows for
-an incorrect implementation in which recent-cpu and priorities are
-updated only for those threads that are on the alarm list or the ready
-list.
-
-The todo item would be a test where a thread is blocked on a
-semaphore, lock or condition variable and have its recent_cpu decay to
-zero, and check that it's scheduled right after the unlock/up/signal.
-
-From: "Godmar Back" <godmar@gmail.com>
-Subject: set_priority & donation - a TODO item
-To: "Ben Pfaff" <blp@cs.stanford.edu>
-Date: Mon, 20 Feb 2006 22:20:26 -0500
-
-Ben,
-
-it seems that there are currently no tests that check the proper
-behavior of thread_set_priority() when called by a thread that is
-running under priority donation.  The proper behavior, I assume, is to
-temporarily drop the donation if the set priority is higher, and to
-reassume the donation should the thread subsequently set its own
-priority again to a level that's lower than a still active donation.
-
- - Godmar
-
-From: Godmar Back <godmar@gmail.com>
-Subject: project 4 question/comment regarding caching inode data
-To: Ben Pfaff <blp@cs.stanford.edu>
-Date: Sat, 14 Jan 2006 15:59:33 -0500
-
-Ben,
-
-in section 6.3.3 in the P4 FAQ, you write:
-
-"You can store a pointer to inode data in struct inode, if you want,"
-
-Should you point out that if they indeed do that, they likely wouldn't
-be able to support more than 64 open inodes systemwide at any given
-point in time.
-
-(This seems like a rather strong limitation; do your current tests
-open more than 64 files?
-It would also point to an obvious way to make the projects harder by
-specifically disallowing that inode data be locked in memory during
-the entire time an inode is kept open.)
-
- - Godmar
-

 From: Godmar Back <godmar@gmail.com>
 Subject: on caching in project 4
 To: Ben Pfaff <blp@cs.stanford.edu>
 From: Godmar Back <godmar@gmail.com>
 Subject: on caching in project 4
 To: Ben Pfaff <blp@cs.stanford.edu>


@@ -177,13 +55,6 @@ the same performance, which raises the suspicion that the test
 workload might not force any cache replacement, so the eviction
 strategy doesn't matter.)
 
 workload might not force any cache replacement, so the eviction
 strategy doesn't matter.)
 

-Godmar Back <godmar@gmail.com> writes:
-
-> in your sample solution to P4, dir_reopen does not take any locks when
-> changing a directory's open_cnt. This looks like a race condition to
-> me, considering that dir_reopen is called from execute_process without
-> any filesystem locks held.
-

 * Get rid of rox--causes more trouble than it's worth
 
 * Reconsider command line arg style--confuses everyone.
 * Get rid of rox--causes more trouble than it's worth
 
 * Reconsider command line arg style--confuses everyone.


@@ -203,20 +74,6 @@ via Godmar Back:
 
 * Internal tests.
 
 
 * Internal tests.
 

-* Improve automatic interpretation of exception messages.
-
-* Userprog project:
-
-  - Mark read-only pages as actually read-only in the page table.  Or,
-    since this was consistently rated as the easiest project by the
-    students, require them to do it.
-
-  - Don't provide per-process pagedir implementation but only
-    single-process implementation and require students to implement
-    the separation?  This project was rated as the easiest after all.
-    Alternately we could just remove the synchronization on pid
-    selection and check that students fix it.
-

 * Filesys project:
 
   - Need a better way to measure performance improvement of buffer
 * Filesys project:
 
   - Need a better way to measure performance improvement of buffer


@@ -236,14 +93,10 @@ via Godmar Back:
 
   - Add extra credit:
 
 
   - Add extra credit:
 

-    . Low-level x86 stuff, like paged page tables.
-

     . Specifics on how to implement sbrk, malloc.
 
     . Other good ideas.
 
     . Specifics on how to implement sbrk, malloc.
 
     . Other good ideas.
 

-    . opendir/readdir/closedir
-

     . everything needed for getcwd()
 
 To add partition support:
     . everything needed for getcwd()
 
 To add partition support: